Image display apparatus

ABSTRACT

A projector (image display apparatus) having enhanced visual mute or A/V mute functions includes a light modulation element for displaying an image, a lamp for illuminating the light modulation element, and a fan for cooling the lamp; the image display apparatus further includes a visual mute means for setting a visual mute mode in which no image or a predetermined image is displayed on a display screen thereof, and a lamp output luminance adjusting means for adjusting the output luminance of the lamp in response to the setting and canceling of the visual mute mode by the visual mute means.

This is a Continuation of application Ser. No. 10/379,576 filed Mar. 6,2003. The disclosure of the prior application is hereby incorporated byreference herein in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an image display apparatus, and, morespecifically, to a projector including an image display element, a lampfor illuminating the image display element, and a fan for cooling thelamp. The invention also relates to a technique for setting a mode inwhich no image or a predetermined image is displayed on a display screenof the image display apparatus, without stopping the action of the lamp,and to a technique for canceling such setting.

2. Description of the Related Art

Generally, in a projector of the related art, when the user selects amode to display no image, or a predetermined image on a display screen(hereinafter referred to as “Visual Mute Mode”), keeping a main powersupply in the ON-state, a blackened image is displayed on the displayscreen, or an image of a desired logo, for example, is displayed on thedisplay screen. In such case, an audio output is also stopped(hereinafter referred to as “Audio Mute”). Such muting function isespecially effective in the case of a presentation and the like. TheVisual Mute and the Audio Mute are collectively referred to as “A/VMute”, hereinafter.

However, in the related art, luminance intensity of the illuminationlamp is maintained even during the visual mute mode or the A/V Mutemode. Therefore, when a blackened image is displayed on the displayscreen of the image display element, illumination light is transmittedthrough the display screen and thus the image on the display screencannot be made completely black. Further, since the cooling fan keepsoperating, undesired sound of the fan stands out, and thus the effect ofthe visual mute or the A/V mute is not achieved sufficiently.

On the other hand, if the illumination lamp is turned OFF when settingthe visual mute mode or the A/V mute mode, it takes too long to restorethe display in the case of canceling the setting of the mode. This isbecause an extra-high pressure mercury lamp is used as a light source ofthe projector because of its high luminous efficacy and short arclength.

Since the extra-high pressure mercury lamp emits light by evaporatingmercury encapsulated in a light-emitting tube, it takes a long timeuntil mercury is heated up and completely vaporized, and it needs notless than 1 minute until it becomes stable. In addition, a temperatureof the outer wall of the light-emitting tube is kept at about 600° C.,and a vapor pressure of mercury is also high while the extra-highpressure mercury lamp is generating light, so that the temperature andthe internal pressure of the light-emitting tube are not decreasedimmediately even when the lamp is turned OFF. Therefore, electrons canhardly move from cathode to anode even when high voltage at a highfrequency is applied in such state, so that discharge cannot be startedsoon in the tube. As a consequence, it is impossible to relight the lampimmediately. It takes several minutes until mercury is restored to aliquid state in which the lamp is ready to relight. Therefore, switchingthe mode of the display screen between a display mode and the visualmute mode as desired by turning the lamp ON and OFF requires a longwaiting time, and hence is inappropriate in terms of users'environments.

SUMMARY OF THE INVENTION

In view of such problems, an object of the invention is to provide animage display apparatus wherein the output luminance of the lamp and theundesired sound of the fan are suitably lowered when setting the visualmute mode or the A/V mute mode, so that the effect of the setting of themode may be heightened. It is another object of the invention to providean image display apparatus that is able to restore the normal displayquickly when the setting of such a mute mode is canceled.

In order to cope with the problems described above, the inventionemploys the following construction.

The invention provides an image display apparatus including a lightmodulation element for image display, a lamp for illuminating the lightmodulation element, and a fan for cooling the lamp, wherein the imagedisplay apparatus includes visual mute means for setting a visual mutemode in which no image or a predetermined image is displayed on adisplay screen of the image display apparatus, and lamp output luminanceadjusting means for adjusting the output luminance of the lamp inresponse to the setting of the visual mute mode and the cancellation ofthe setting by the visual mute means. Accordingly, the lamp luminancecan be determined appropriately in accordance with the environment whensetting the visual mute mode.

Preferably, the lamp output luminance adjusting means functions in sucha manner that the output luminance of the lamp is lowered in accordancewith the setting of the visual mute mode by the visual mute means, andthe output luminance of the lamp is restored to a state before settingthe visual mute mode in accordance with the cancellation of the setting.In this arrangement, when the image display apparatus is in the visualmute mode, the visual mute is effectively achieved by eliminating theinfluence of the illumination light on the display screen, and when thevisual mute mode is cancelled, the normal image can be displayed quicklyon the screen.

The image display apparatus of the invention includes fan speedadjusting means for adjusting the revolution speed of the fan inresponse to the setting of the visual mute mode and the cancellation ofthe setting by the visual mute means. In this arrangement, therevolution speed of the fan can be determined appropriately inaccordance with the environment when setting the visual mute mode.

Preferably, the fan speed adjusting means functions in such a mannerthat the revolution speed of the fan decreases in accordance with thesetting of the visual mute mode by the visual mute means, and isrestored to a state before the setting of the visual mute mode inaccordance with the cancellation of the setting. In this arrangement,when the image display apparatus is in the visual mute mode, the visualmute is effectively achieved by reducing the revolution speed of the fanand hence reducing its undesired sound, and when the visual mute mode iscancelled, the revolution speed of the fan can be restored to therevolution speed under normal control.

The image display apparatus of the invention further includes a speakerfor outputting sound, and an audio adjusting means (for A/V Mutefunction) for adjusting the output of the speaker in response to thesetting of the visual mute mode and the cancellation of the setting bythe visual mute means. Accordingly, when the visual mute mode is set,the output volume from the speaker can be determined appropriatelyaccording to the environment.

Preferably, the audio adjusting means functions in such a manner thatthe output of the speaker is stopped in accordance with the setting ofthe visual mute mode by the visual mute means, and the output of thespeaker is restored in accordance with the cancellation of the setting.In this arrangement, when the image display apparatus is in the visualmute mode, the audio output is completely stopped, and when the visualmute mode is cancelled, the sound can be quickly output in accordancewith the normal image display.

The construction described above is especially effective when it isemployed in a projector. This is because recent projectors employ anextra-high pressure mercury lamp having characteristics as describedabove as a light source in many cases.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a principal construction of a singlepanel projector according to an embodiment of the invention;

FIG. 2 is a flow chart showing the action relating to setting of an A/Vmute mode (involving non-display of image and non-output of sound) ofthe projector shown in FIG. 1;

FIG. 3 is a timing chart showing the actions of the lamp in the caseswhere a visual mute mode is set and cancelled, comparing between thecase of this embodiment and the case where the lamp is turned OFF/ON;

FIG. 4 is a block diagram showing a principle construction of athree-panel projector relating to the second embodiment of theinvention; and

FIG. 5 is a block diagram showing an optical system of the projector inFIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment

FIG. 1 is a block diagram showing a principal construction of a singlepanel projector for describing an embodiment of the invention. Anprojector 100 includes, as shown in the figure, a lamp 1 as anillumination light source, a light modulation element 2 such as a liquidcrystal panel being illuminated by the lamp 1 and displaying imagesbased on predetermined image information, and a projection lens 3 forprojecting the images generated by the light modulation element 2. Theprojector 100 also includes a lamp driving circuit 1A for driving thelamp 1, an image processing circuit 2A for supplying image informationto the light modulation element 2, a speaker 4 for outputting sound, anaudio processing circuit 4A for supplying audio information to thespeaker 4, a fan 5 for cooling the lamp 1 and/or the light modulationelement 2, a fan driving circuit 5A for driving the fan 5, a userinterface 6 including an input device for supplying various controlinformation and data to the projector 100, and a central processing unit(CPU) 7 for monitoring and controlling the lamp driving circuit 1A, theimage processing circuit 2A, the audio processing circuit 4A, the fandriving circuit 5A, and the user interface 6.

The lamp driving circuit 1A, the image processing circuit 2A, the audioprocessing circuit 4A, the fan driving circuit 5A, and the userinterface 6 are briefly described here.

The lamp driving circuit 1A is a power source circuit for supplying adriving power to the lamp 1. The amount of power to be supplied to thelamp 1 by the lamp driving circuit 1A is controlled by the CPU 7,whereby the output luminance of the lamp 1 is adjusted.

The image processing circuit 2A reads signals of an image displayed on apersonal computer or stored therein in advance, and supplies them as RGBsignals to the light modulation element 2. Various settings fordisplaying images are also made by the image processing circuit 2A. Theimage processing circuit 2A is also controlled by the CPU 7.

The audio processing circuit 4A processes audio signals loaded withimages to output them through the speaker 4, and the ON-OFF state of theaudio output to the speaker 4 is controlled by the CPU 7.

The fan driving circuit 5A supplies a power to the fan 5 for blowingcooling air to the lamp 1 and/or the light modulation element 2, and theamount of power to be supplied is controlled by the CPU 7. Since therecent high luminance lamp generates considerable heat when in use, itis important to cool the lamp down.

The user interface 6 is for inputting various control information orvarious data from the outside to the projector 100. Loading of imagesignals from the external personal computer or image signals to bepreparedly stored in the projector is performed through the userinterface 6. Instructions of various mute settings (or selections) maybe performed by the user interface 6.

In the projector 100, while the main power source is ON, the lamp 1 isturned on by the lamp driving circuit 1A and the illumination of thelamp 1 enters into the light modulation element 2. The light modulationelement 2 receiving the illumination light from the lamp 1 displays animage on its display screen based on image information sent from theimage processing circuit 2A, and the image is projected on a screen 200via the projection lens 3. In association with the image display, asound is output from the speaker 4 based on audio information suppliedby the audio processing circuit 4A. When the main power supply is turnedON, the fan 5 is driven by the fan driving circuit 5A, so that atemperature of the inside of the projector is kept below a predeterminedvalue. The driving of the fan 5 is automatically controlled by the CPU 7in accordance with temperatures inside the projector in general cases.

Subsequently, the action relating to the A/V mute (non-display of imageand non-output of sound) function of the projector 100 and the settingof A/V mute mode will be described based on the flow chart shown in FIG.2.

When the main power supply of the projector is ON, whether or notselection of A/V mute mode is input through the user interface 6 ismonitored (step S1). As a result of monitoring, when the selection ofA/V mute mode is not input, the lamp 1, the light modulation element 2,and the speaker 4 are operated by normal control, so that the imagedisplay and audio output is achieved (Step S2 and S3).

In contrast, when it is determined that the selection of A/V mute modeis input in Step S1, an image preselected by the user is displayed onthe display screen of the light modulation element 2 (Step S4). Theselected image may be any image such as a blackened image making theentire display screen black, or a logo image preset by the user.

Subsequently, the lamp drive circuit 1A is controlled to lower theluminance of the lamp 1 to a degree that does not allow the illuminationlight to transmit through the display screen of the light modulationelement 2 (Step S5).

The fan driving circuit 5A is controlled to reduce the revolution speedof the fan 5 to a degree that its undesired sound does not bother theviewer (Step S6).

Furthermore, the audio processing circuit 4A is controlled to stop theaudio output from the speaker 4 (Step S7). The amount of reduction ofthe output luminance of the lamp 1 or the amount of reduction of therevolution speed of the fan 5 at the time when the A/V mute mode isselected may be adjusted as appropriate in accordance with theenvironment and the object without being limited to the exampledescribed above.

After the process from Step S4 to S7 is terminated, whether or not thecancellation of the A/V mute mode is input through the user interface 6is monitored (Step S8). When the A/V mute mode is still selected, theA/V mute setting described above is maintained.

In contrast to it, when it is determined that the cancellation of theA/V mute mode is input in Step S8, the lamp driving circuit 1A iscontrolled to restore the luminance of the lamp 1 to a state beforesetting to the A/V mute mode (Step S9).

The revolution speed of the fan 5 is restored to a state under normalcontrol that controls in accordance with a temperature of the inside ofthe projector (Step S10). In this case, the revolution speed of the fan5 may be restored to a state before setting to the A/V mute mode.

Then, information of the image displayed before setting to the A/V mutemode or new image information designated by the user is supplied fromthe image processing circuit 2A to the light modulation element 2, so asto display the image on the display screen of the light modulationelement 2 (Step S11).

Further, the audio processing circuit 4A is controlled to be restored toa state before setting to the A/V mute mode so as to output the soundthrough the speaker 4 (Step S12).

“Monitoring”, “determination”, and “control” in the steps describedabove are performed by the CPU 7.

When it is determined that the selection of the A/V mute mode is inputin the steps described above, the display screen may be set to thenon-display mode (screen display OFF) instead of displaying an imagepreselected by the user on the display screen of the light modulationelement 2.

Furthermore, the order of the steps S4 to S7 at the time when the A/Vmute mode is selected, or the order of the steps S9 to S12 at the timewhen the A/V mute mode is cancelled may be modified, or may be performedsimultaneously.

FIG. 3 is a timing chart showing the actions of the lamp 1 in the caseswhere the A/V mute mode is selected and cancelled, comparing between thecase of this embodiment and the case where the lamp 1 is turned OFF/ON.

It is ideal that the luminance of the lamp 1 is varied concurrently(graph b) with the selection and cancellation of the A/V mute mode bythe user (graph a). However, it is impossible in the case where theextra-high pressure mercury lamp is employed. For example, in the casewhen the extra-high pressure mercury lamp is turned OFF by selecting theA/V mute mode, when the A/V mute mode is cancelled to relight the lampagain, it requires about one minute for cooling off the lamp and anotherthirty seconds or so for recovering the luminance of the lamp to thestate before the mute mode (graph c).

In contrast to it, in this embodiment in which the lamp 1 is adjusted toreduce its output luminance by a certain amount without turning off thelamp 1, when the A/V mute mode is selected, the luminance of the lamp 1is reduced almost concurrently, and when the A/V mute mode is cancelled,the luminance can be recovered to the state before the mute mode withabout one second of delay (graph d). Accordingly, the viewer rarelyfeels delay of image display when the A/V mute mode is cancelled. It isbecause mercury in the lamp once turned on is kept in the vaporizedstate and the internal pressure is sufficiently high when the mute modeis switched (selected), whereby the luminance can be changed furtherquicker than the case where it is first turned ON.

Second Embodiment

FIG. 4 is a block diagram showing a principle construction of athree-panel projector for describing the second embodiment of theinvention. A projector 300 separates illumination light from a lamp unit13 into red light (R), green light (G), and blue light (B) using acolored light separating optical system 8, projects the separatedcolored lights on liquid crystal panels 2R, 2G and 2B, which are lightmodulation elements provided for the respective RGB signals of an image,to display images thereon, combines the respective colored images by across dichroic prism 9, and projects a combined image through theprojection lens 3. In FIG. 4, the same reference numerals as FIG. 1 showidentical or corresponding components in FIG. 1.

(i) Construction Relating to the A/V Mute Function

In this three-panel projector 300, when the A/V mute mode is set,signals of no image or a predetermined image are sent to the respectiveliquid crystal panels 2R, 2G, 2B from the image processing circuit 2A todisplay the image. When the A/V mute mode is cancelled, a process torestore the normal image display is performed on the respective liquidcrystal panels. The setting and processes other than these are basicallythe same as the case of the first embodiment. Therefore, the actionprocess relating to the setting of the A/V mute mode in the secondembodiment is performed in accordance with the flowchart in FIG. 2.

(ii) Construction of the Optical Unit

FIG. 5 is a block diagram showing an optical system of the projector300. Referring to FIG. 5, the construction and the operation of theoptical unit of the projector 300 will be described below.

This optical unit includes an illumination optical system 23, thecolored light separating optical system 8, a relay optical system 25,the liquid crystal panels 2R, 2G and 2B as light modulation units, thecross dichroic prism 9 for combining colored lights, the projection lens3, and so on.

The illumination optical system 23 includes the lamp unit 13 including alamp 11 and a reflector 12, a first and a second lens arrays 21, 22constituting an integrator lens for almost uniformly illuminating theimage forming areas of the liquid crystal panels 2R, 2G and 2B, areflecting mirror 31 (this is not necessary in the case of a layoutwhere the direction of travel of the illumination light is not changed),and a superimposed lens 32.

The first lens array 21 has a construction including small lenses 211that are substantially rectangular in profile disposed into a matrix ofM rows×N columns. The respective small lenses 211 divide parallel lightfluxes incoming from the lamp 1 into a plurality (M×N) of partial lightfluxes, and allow the respective partial light fluxes to form images inthe vicinity of the second lens array 22. The shape of each small lens211 is determined to be similar to the shape of the image forming areasof the liquid crystal panels 2R, 2G and 2B. For example, when the aspectratio (ratio between the width and the height) of the image forming areaof the liquid crystal panel is 4:3, the aspect ratio of each small lensis set to 4:3 as well.

The second lens array 22 has a construction in which small lenses 221are disposed into a matrix of M rows×N columns corresponding to thesmall lenses 211 of the first lens array 21.

The colored light separating optical system 8 includes two dichroicmirrors 41 and 42, and a reflecting mirror 43, and has a function forseparating a light projected from the superimposed lens 32 of theillumination optical system 23 into red, green, and blue light.

The relay optical system 25 is an optical path for light transmittedfrom the dichroic mirror 42, and includes a lens 54 on the incidentside, reflecting mirrors 71 and 72, and a relay lens 73.

The liquid crystal panels 2R, 2G and 2B employ, for example, polysiliconThin-Film-Transistor (TFT) as switching elements, and are fixedly bondedto the cross dichroic prism 9 via fixing members so as to face towardthree side surface of the cross dichroic prism 9. Incident-sidepolarizing plates 60R, 60G, and 60B are disposed on the side of thelight incident and outgoing plane of the liquid crystal panels 2R, 2Gand 2B, and outgoing-side polarizing plates 61R, 61G and 61B aredisposed on the outgoing-side thereof.

The cross dichroic prism 9 is for forming a colored image by combiningred, green and blue lights, and is formed with a dielectric materialmulti-layer film for reflecting red light and a dielectric materialmulti-layer film for reflecting blue right in a substantially X-shapealong the interfaces of four rectangular prism. These dielectricmaterial multi-layer films combine these three colored lights. Theprojection lens 3 is disposed on the outgoing-side of the cross dichroicprism 9.

(iii) Action of the Optical Unit

Light projected from the lamp 11 is reflected by the reflector 12, andenters into an integrator lens including the first and the second lensarrays 21, 22. Images to be formed by the respective lens cells of thefirst lens array 21 are focused on the display surface of the respectiveliquid crystal panels 2R, 2G and 2B by the second lens array 22 and thesuperimposed lens 32, so that the integrator lens carries out thefunctions to improve the efficiency of light utilization and eliminateunevenness of illumination on the surface of the liquid crystal panels.Light outgoing from the integrator lens and the superimposed lens 32subsequently enters into the colored light separating optical system 8.

The first dichroic mirror 41 of the colored light separating opticalsystem 8 reflects red light component and transmits blue light componentand green light component of the light flux projected by theillumination optical system 23. Red light reflected from the firstdichroic mirror 41 enters into a field lens 51 through the reflectingmirror 43, and reaches the liquid crystal panel 2R for red light. Thefield lens 51 converts the respective separated light fluxes projectedfrom the second lens array 22 into fluxes in parallel with the centralaxis (main light beam). Other field lenses 52, 53 provided in front ofother liquid crystal panels 2G and 2B act in the same manner.

Green light out of blue light and green light passed through the firstdichroic mirror 41 is reflected by the second dichroic mirror 42, passesthrough the field lens 52, and reaches the liquid crystal panel 2G forgreen right. On the other hand, blue light passes through the seconddichroic mirror 42, the relay optical system 25, and further the fieldlens 53, and reaches the liquid crystal panel 2B for blue light.

The respective lights in red, green and blue separated by the coloredlight separating optical system 8 are converted into specific polarizedlights by the incident-side polarizing plates 60R, 60G and 60B beforeentering into the liquid crystal panels 2R, 2G and 2B. Subsequently, therespective polarized lights are modulated in the respective liquidcrystal panels 2R, 2G and 2B based on image information given by theimage processing apparatus 2A, and projected to the outgoing-sidepolarized plates 61R, 61G and 61B as modulated lights. Only specialpolarized light of the modulated light passes through the outgoing-sidepolarizing plates 61R, 61G and 61B, and enters into the cross dichroicprism 9. The respective colored lights are combined in the crossdichroic prism 9 into a combined light, and projected from theprojection lens 3 onto the screen 200 as a color image.

When a polarized beam splitter for converting illuminating lightincluding both P-polarized light and S-polarized light from the lampunit 13 into any one of those polarized light is disposed at thepredetermined position of the illumination optical system 23, forexample, between the second lens array 22 and the superimposed lens 32,almost all the light incoming from the lamp unit 13 may be utilizedwithout being wasted in the liquid crystal panels 2R, 2G and 2B.

In the above embodiments, the single panel projector having one lightmodulation element and the three-panel projector having three liquidcrystal panels corresponding to the respective RGB signals have beendescribed as examples. However, any number, such as two or four, of thelight modulation elements such as liquid crystal panels may be used.

Although the liquid crystal panel employed in this embodiment is atransmitting type that transmits and modulates light, it may be the typethat modulates incoming light while reflecting, and projects themodulated light.

Furthermore, the projector may be any type including a front projectingtype that projects on the front surface of the screen and the rearprojecting type that projects from the backside of the screen.

In the above embodiments, the visual mute and the output luminancecontrol of the lamp, the audio mute, and speed adjustment of the fan areperformed altogether when setting the A/V mute mode. However, it is alsopossible to combine the set of the visual mute and the output luminancecontrol of the lamp only with the audio mute, or to combine the set onlywith the speed adjustment of the fan.

Furthermore, although an example in which the visual mute function orA/V mute function are applied to the projector has been described in theabove-described embodiments, the invention is not limited to theprojector, and it is applicable also to other image display apparatususing a lamp such as an extra-high pressure mercury lamp that requires arelatively long time before illuminating. In this case, preferably, theoutput luminance of the lamp or the revolution of the fan at the timingof setting the mute mode may be determined appropriately depending onthe environment of the image display apparatus.

According to the image display apparatus of the invention, since theluminance of the lamp is reduced and the undesired sound of the fan isalso reduced when the visual mute mode or A/V mute mode is set, theinfluence of light or sound on the viewer is alleviated, and thus theeffect of these muting function may be increased. In addition, whencanceling the muting mode, the normal screen may quickly be displayed.

1. An image display apparatus comprising: a light modulation element forimage display; a lamp for illuminating the light modulation element; anda fan for cooling the lamp; wherein the image display apparatuscomprises: a visual mute means for setting a visual mute mode in whichno image or a predetermined image is displayed on a display screen ofthe image display apparatus; and a lamp output luminance adjusting meansfor adjusting the output luminance of the lamp in response to thesetting of the visual mute mode and the cancellation of the setting bythe visual mute means.